With the increasing down-scaling of integrated circuits and increasingly demanding requirements to the speed of integrated circuits, transistors need to have higher drive currents with smaller dimensions. Fin field-effect transistors (fin-FET) were thus developed. Fin-FET transistors have increased channel widths. Since the drive currents of transistors are proportional to the channel widths, the drive currents of fin-FETs are increased. To maximize the channel width of a fin-FET, the fin-FET may include multiple fins, with the ends of the fins connected to a same source and a same drain. The formation of multi-fin fin-FET may include forming a plurality of fins parallel to each other, forming a gate stack on the plurality of fins, and interconnecting the ends of the plurality of fins to form a source region and a drain region. The forming of the gate stack may include depositing layers of material on the fins and patterning the deposited layers to form the gate stack. Several multi-fin fin-FETs may be formed next to each other on a substrate which may include a dummy gate stack between fin-FETs to aid in certain processing steps.
However, due to the integral fin numbers, the fin-FET N/P strength ratio (ratio of N-type fin-FETs to P-type fin-FETS) is difficult to tune. Additionally, designers typically demand varied N/P ratios for different circuits. In conventionally FETs, the FET width would be used to tune the N/P strength ratio. By varying the width of the FET portion, the strength ratio can be tuned to the desired strength ratio.
Accordingly, there is a need for systems, apparatus, and methods that improve upon conventional approaches including the improved methods, systems and apparatus provided hereby.
The inventive features that are characteristic of the teachings, together with further features and advantages, are better understood from the detailed description and the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and does not limit the present teachings.